Assadullah Khalid, head of Afghanistan's National Directorate of Security (NDS) and a confidant of Karzai, was injured in Thursday's attack in a guest house of the spy agency in Kabul.

Taliban claimed responsibility for the attack in revenge for the recent execution of several Taliban prisoners, saying the attacker posed as a peace messenger.

On Saturday, Karzai, however, ruled out the possibility of Taliban's involvement in the attack, saying it was impossible for Taliban to carry out what he described as a "complicated attack".

He alleged that the attack was planned by Pakistan-based militants and called for investigation to ascertain the attackers.

Pakistan, however, asked Kabul to share intelligence with Pakistan instead of levelling charges.

"Before levelling charges the Afghan government would do well if they shared information or evidence with the government of Pakistan that they might have with regard to the cowardly attack on the head of NDS.

"They would also do well by ordering an investigation into any lapses in the security arrangements around the NDS chief," Pakistan's foreign ministry said.